25 research outputs found
Semiring-based constraint logic programming
We extend the Constraint Logic Programming (CLP) formalism in order to handle semiring-based constraints. This allows us to perform in the same language both constraint solving and optimization. In fact, constraints based on semirings are able to model both classical constraint solving and more sophisticated features like uncertainty, probability, fuzziness, and optimization. We then provide this class of languages with three equivalent semantics: model-theoretic, fix-point, and proof-theoretic, in the style of classical CLP programs
A Declarative Semantics for CLP with Qualification and Proximity
Uncertainty in Logic Programming has been investigated during the last
decades, dealing with various extensions of the classical LP paradigm and
different applications. Existing proposals rely on different approaches, such
as clause annotations based on uncertain truth values, qualification values as
a generalization of uncertain truth values, and unification based on proximity
relations. On the other hand, the CLP scheme has established itself as a
powerful extension of LP that supports efficient computation over specialized
domains while keeping a clean declarative semantics. In this paper we propose a
new scheme SQCLP designed as an extension of CLP that supports qualification
values and proximity relations. We show that several previous proposals can be
viewed as particular cases of the new scheme, obtained by partial
instantiation. We present a declarative semantics for SQCLP that is based on
observables, providing fixpoint and proof-theoretical characterizations of
least program models as well as an implementation-independent notion of goal
solutions.Comment: 17 pages, 26th Int'l. Conference on Logic Programming (ICLP'10
ASP(AC): Answer Set Programming with Algebraic Constraints
Weighted Logic is a powerful tool for the specification of calculations over
semirings that depend on qualitative information. Using a novel combination of
Weighted Logic and Here-and-There (HT) Logic, in which this dependence is based
on intuitionistic grounds, we introduce Answer Set Programming with Algebraic
Constraints (ASP(AC)), where rules may contain constraints that compare
semiring values to weighted formula evaluations. Such constraints provide
streamlined access to a manifold of constructs available in ASP, like
aggregates, choice constraints, and arithmetic operators. They extend some of
them and provide a generic framework for defining programs with algebraic
computation, which can be fruitfully used e.g. for provenance semantics of
datalog programs. While undecidable in general, expressive fragments of ASP(AC)
can be exploited for effective problem-solving in a rich framework. This work
is under consideration for acceptance in Theory and Practice of Logic
Programming.Comment: 32 pages, 16 pages are appendi
Soft Constraint Programming to Analysing Security Protocols
Security protocols stipulate how the remote principals of a computer network
should interact in order to obtain specific security goals. The crucial goals
of confidentiality and authentication may be achieved in various forms, each of
different strength. Using soft (rather than crisp) constraints, we develop a
uniform formal notion for the two goals. They are no longer formalised as mere
yes/no properties as in the existing literature, but gain an extra parameter,
the security level. For example, different messages can enjoy different levels
of confidentiality, or a principal can achieve different levels of
authentication with different principals.
The goals are formalised within a general framework for protocol analysis
that is amenable to mechanisation by model checking. Following the application
of the framework to analysing the asymmetric Needham-Schroeder protocol, we
have recently discovered a new attack on that protocol as a form of retaliation
by principals who have been attacked previously. Having commented on that
attack, we then demonstrate the framework on a bigger, largely deployed
protocol consisting of three phases, Kerberos.Comment: 29 pages, To appear in Theory and Practice of Logic Programming
(TPLP) Paper for Special Issue (Verification and Computational Logic
Quantitative mu-calculus and CTL Based on Constraint Semirings
Model checking and temporal logics are boolean. The answer to the model checking question does a system satisfy a property? is either true or false, and properties expressed in temporal logics are defined over boolean propositions. While this classic approach is enough to specify and verify boolean temporal properties, it does not allow to reason about quantitative aspects of systems. Some quantitative extensions of temporal logics has been already proposed, especially in the context of probabilistic systems. They allow to answer questions like with which probability does a system satisfy a property?
We present a generalization of two well-known temporal logics: CTL and the [mu]-calculus. Both extensions are defined over c-semirings, an algebraic structure that captures many problems and that has been proposed as a general framework for soft constraint satisfaction problems (CSP). Basically, a c-semiring consists of a domain, an additive operation and a multiplicative operation, which satisfy some properties. We present the semantics of the extended logics over transition systems, where a formula is interpreted as a mapping from the set of states to the domain of the c-semiring, and show that the usual connection between CTL and [mu]-calculus does not hold in general. In addition, we reason about the feasibility of computing the logics and illustrate some applications of our framework, including boolean model checking
Ordering based decision making: a survey
Decision making is the crucial step in many real applications such as organization management, financial planning, products evaluation and recommendation. Rational decision making is to select an alternative from a set of different ones which has the best utility (i.e., maximally satisfies given criteria, objectives, or preferences). In many cases, decision making is to order alternatives and select one or a few among the top of the ranking. Orderings provide a natural and effective way for representing indeterminate situations which are pervasive in commonsense reasoning. Ordering based decision making is then to find the suitable method for evaluating candidates or ranking alternatives based on provided ordinal information and criteria, and this in many cases is to rank alternatives based on qualitative ordering information. In this paper, we discuss the importance and research aspects of ordering based decision making, and review the existing ordering based decision making theories and methods along with some future research directions
A Transformation-based Implementation for CLP with Qualification and Proximity
Uncertainty in logic programming has been widely investigated in the last
decades, leading to multiple extensions of the classical LP paradigm. However,
few of these are designed as extensions of the well-established and powerful
CLP scheme for Constraint Logic Programming. In a previous work we have
proposed the SQCLP (proximity-based qualified constraint logic programming)
scheme as a quite expressive extension of CLP with support for qualification
values and proximity relations as generalizations of uncertainty values and
similarity relations, respectively. In this paper we provide a transformation
technique for transforming SQCLP programs and goals into semantically
equivalent CLP programs and goals, and a practical Prolog-based implementation
of some particularly useful instances of the SQCLP scheme. We also illustrate,
by showing some simple-and working-examples, how the prototype can be
effectively used as a tool for solving problems where qualification values and
proximity relations play a key role. Intended use of SQCLP includes flexible
information retrieval applications.Comment: 49 pages, 5 figures, 1 table, preliminary version of an article of
the same title, published as Technical Report SIC-4-10, Universidad
Complutense, Departamento de Sistemas Inform\'aticos y Computaci\'on, Madrid,
Spai